The invention relates generally to a computer-implemented method for booting a computer system, and more specifically, to a resource-based boot sequence. The invention relates further to a related boot module for booting a computer system, and a computer program product. Today's computing centers—in particular cloud computing centers and also hybrid approaches—rely heavily on virtual machines as a key delivery mechanism for providing ad-hoc IT (information technology) resources for pilot projects, testing purposes and also for production environments. In such a context, it is paramount to set up virtual machines in virtually no time, i.e., the time required for booting the virtual machine becomes a critical parameter.
Today, upon a boot request for a virtual machine, the virtual machine is constructed with all resources available, i.e., after all requested virtual CPUs, memory resources and devices are available for the new virtual machine. This may cause some delays in booting the virtual machine. Given the sheer size of today's systems—e.g., terabytes of memory, hundred or more CPUs, and so on—it becomes uneconomical to firstly construct the container for the virtual machine with all resources before booting the system because it may imply clearing a terabyte of requested memory. On the other hand, booting a system of virtual machines before all resources are available may cause unexpected failures during the startup of services. A simple example may be an out-of-memory situation due to the fact that at a certain point in time, during the boot process, sufficient memory is not available.